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In general, the present invention is directed towards a spontaneous combustion process and apparatus. More particularly, the present invention discloses a process and apparatus whereby flameless combustion may be precipitated and maintained within an essentially oval combustion chamber of an integrated heater/burner apparatus absent catalyst or high temperature oxidant.
Conventional furnaces and industrial heaters operate at sufficiently high flame temperatures to form nitrogen oxides, sometimes referred to as oxides of nitrogen or NOx. A thermal combustion system of the contemporary art typically operates by contacting fuel and air in flammable portions with an ignition source and ignites this mixture which then continues to burn. Flammable mixtures of most fuels are normally designed to burn at relatively high temperatures, of approximately 3300xc2x0 F. and above, which inherently result in the formation of substantial amounts of NOx.
Industrial heaters are well known and represented in the contemporary art. The science and practice of flameless combustion is equally well known and appreciated by those skilled in the art. What is not known is the novel combination of flameless combustion within an essentially oval (as used herein the term xe2x80x9covalxe2x80x9d is used synonymously and interchangeably with xe2x80x9croundxe2x80x9d or xe2x80x9ccircularxe2x80x9d and is intended to encompass any and all combustion chamber configurations allowing for sufficient recirculation of gases to facilitate practice, disclosure and claims of the instant invention) heater to facilitated increased recirculation rates of hot flue gas, fuel gas and air within the heater""s radiant section to achieve and maintain flameless combustion and then utilizing increased amounts of flue gas recirculation at increased temperature to allow flue gas to be mixed with fuel gas and combustible air at significantly higher percentages than is possible in the prior art. In the instant invention, ribbons of fuel gas, recirculated flue gas and combustion air are combined within a narrowly defined boundary reach auto ignition temperature and precipitate the combustion process. However, due to the essentially oval character of the internal portion of the instant invention""s combustion chamber, the mass flow of recirculated flue gas can be of sufficient quantity to allow gases involved in the combustion process to limitedly experience a temperature variation between approximately 300xc2x0 to 400xc2x0 F., versus a temperature differential range of 2800xc2x0 F., between the hottest flame temperature and the coolest flue gases in the combustion chamber which is common in existing combustion technology. In the instant invention, the maximum temperature anywhere in the invention""s combustion chamber never exceeds 2200xc2x0 F. Consequently, such reduced temperature virtually eliminates thermal NOx and NOx falls into a selective catalytic reduction range of less than 8 ppmvd. The immediately following table illustrates new window of operation made possible by the apparatus and process of the instant invention. 
Consequently, in view of the deficiencies of the contemporary art, it is an object of the instant invention to disclose and claim a flameless combustion process and apparatus absent involvement of catalyst, high temperature air, or other similarly intended oxidants.
It is a further object of the instant invention to disclose and claim a process and apparatus to achieve flameless combustion with air or other similarly intended oxidant temperatures below 1300xc2x0 F.
It is yet another object of the instant invention to disclose and claim a process and apparatus to achieve flameless combustion absent necessity for catalyst or flame holder.
Another object of the instant invention is to disclose and claim an integrated heater/burner apparatus. As used herein, the term xe2x80x9cheaterxe2x80x9d is defined, used synonymously and interchangeably as xe2x80x9ca refractory lined enclosure containing a heat transfer cooling coilxe2x80x9d and the term xe2x80x9cburnerxe2x80x9d is defined, used synonymously and interchangeably as a metering device for fuel, air and recirculated flue gas.
Another object of the instant invention is to disclose and claim an apparatus which embodies an essentially oval combustion chamber that acts as a means for controlling the rate of diffusion of air, fuel and flue gas.
An additional object of the instant invention is to disclose and claim a means by which very uniform flux rates can be achieved via recirculation rates of flue gas beyond that possible initializing heater/burners of the contemporary unit.
A further object of the instant invention is to eliminate cold and hot zones associated combustion chambers with industrial heaters of the prior art.
Yet an additional object of the instant invention is to teach and claim the heater/burner apparatus of reduced size and cooling coil service area while not increasing peak radiant flux rates.
Another object of the instant invention is to introduce a process and apparatus whereby very uniform and cooler combustion may be precipitated, thus creating low NOx emissions measured at less than 8 ppmvd.
Yet another object of the instant invention is to provide for complete combustion at very uniform and controlled temperatures eliminating CO emissions.
Yet another object of the instant invention is to increase radiant efficiency to reduce fuel consumption which will then reduce CO2 and greenhouse gas emissions.
An additional object of the instant invention is to teach an apparatus and process to improve heat transfer thereby reducing a heater cooling coil area required to achieve a specified amount of heat transfer without exceeding prior art peak radiant flux rates.
Other objects and further scope of the applicability of the present invention will become apparent from the detailed description to follow, taken in conjunction with the accompanying drawings wherein like parts are designated by like reference numerals.
A method and apparatus to precipitate and sustain flameless combustion within an essentially oval combustion of an integrated heater/burner apparatus comprising the steps of (a) providing an essentially oval combustion chamber in communication with an air inlet, the air inlet in further communication with an air source external to said essentially oval chamber; (b) providing a fuel source within said combustion chamber, the fuel source introducing a fuel gas, the fuel gas in communication with a fuel supply and said combustion chamber; (c) initializing a heating process within said chamber to preheat the chamber""s internal portion to an operational temperature generally ranging between 1400xc2x0 F. and 2100xc2x0 F.; (d) introducing air to the oval combustion chamber via said air inlet; (e) precipitating the re-circulation of flue gas within said chamber as a consequence of steps (c) and (d); (f) inerting said fuel gas with said recirculated flue gas; (g) metering and delivering fuel gas to said combustion chamber and fuel gas to be inerted by recirculated flue gas; (h) continuing to meter and heat air, recirculated fuel and flue gas until said air, recirculated fuel and flue gas diffuse into a molecular composite and reach or exceed the auto ignition temperature said composition; and (i) sustaining flameless combustion by maintaining a combustion chamber operational temperature of generally between 1400xc2x0 F. and 2100xc2x0 F.